Image forming apparatus

Abstract

An image forming apparatus includes: an image forming unit including a rotating member and being configured to form an image on a paper sheet in accordance with print job data; a rotation position detecting unit configured to detect a rotation position of the rotating member; an image density detecting unit configured to detect a density in an image formed on an image carrier; an image information analyzing unit configured to analyze image information in the print job data; a density profile managing unit configured to form a correction patch image on the image carrier, and create and manage a density profile indicating periodical density unevenness; a correction data creating unit configured to create correction data; a density correcting unit configured to perform density correction; and a density correction control unit configured to predict an appearance of periodical density unevenness, and set conditions for the density correction.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 an image forming unit including a rotating member as a component, the image forming unit being configured to form an image on a paper sheet in accordance with print job data; 
 a rotation position detecting unit configured to detect a rotation position of the rotating member; 
 an image density detecting unit configured to detect a density in an image formed on an image carrier by the image forming unit; 
 an image information analyzing unit configured to analyze image information included in the print job data; 
 a density profile managing unit configured to form a correction patch image on the image carrier, and create and manage a density profile indicating periodical density unevenness in accordance with a result of the detection performed by the image density detecting unit with respect to the correction patch image; 
 a correction data creating unit configured to create correction data corresponding to the rotation position of the rotating member in accordance with the density profile; 
 a density correcting unit configured to perform density correction using the correction data; and 
 a density correction control unit configured to predict an appearance of periodical density unevenness in accordance with image information about the image to be formed, and set conditions for the density correction in accordance with a result of the prediction; 
 wherein the density correction control unit extracts image regions from the image, determines a reference image region in accordance with lengths of the extracted image regions in a sub-scan direction and densities in the extracted image regions, and sets the conditions for the density correction in accordance with the length of the reference image region in the sub-scan direction and the density in the reference image region; 
 wherein, in accordance with the length of the reference image region in the sub-scan direction and the density in the reference image region, the density correction control unit determines whether to update the correction data; and 
 wherein, when the length of the reference image region in the sub-scan direction is equal to or greater than a cycle length of the rotating member, and a difference between the density in the reference image region and a reference density is equal to or smaller than a predetermined threshold value, the density correction control unit updates the correction data. 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein the image information includes size information, color information, density information, and page information about the image included in the print job data, and size information about the paper sheet on which the image is to be formed. 
     
     
       3. The image forming apparatus according to  claim 1 , wherein, when the length of the reference image region in the sub-scan direction is equal to or greater than a cycle length of the rotating member, a difference between the density in the reference image region and a reference density is equal to or smaller than a predetermined threshold value, and an area ratio of the density in the reference image region is equal to or higher than a predetermined threshold value, the density correction control unit updates the correction data. 
     
     
       4. The image forming apparatus according to  claim 1 , wherein, when updating the correction data, the density correction control unit sets a length of the correction patch image in accordance with the length of the reference image region in the sub-scan direction. 
     
     
       5. An image forming apparatus comprising:
 an image forming unit including a rotating member as a component, the image forming unit being configured to form an image on a paper sheet in accordance with print job data; 
 a rotation position detecting unit configured to detect a rotation position of the rotating member; 
 an image density detecting unit configured to detect a density in an image formed on an image carrier by the image forming unit; 
 an image information analyzing unit configured to analyze image information included in the print job data; 
 a density profile managing unit configured to form a correction patch image on the image carrier, and create and manage a density profile indicating periodical density unevenness in accordance with a result of the detection performed by the image density detecting unit with respect to the correction patch image; 
 a correction data creating unit configured to create correction data corresponding to the rotation position of the rotating member in accordance with the density profile; 
 a density correcting unit configured to perform density correction using the correction data; and 
 a density correction control unit configured to predict an appearance of periodical density unevenness in accordance with image information about the image to be formed, and set conditions for the density correction in accordance with a result of the prediction; 
 wherein the density correction control unit separates the image into respective color components, and sets the conditions for the density correction for each of the color components. 
 
     
     
       6. A non-transitory recording medium storing a computer readable program to be used in an image forming apparatus including an image forming unit configured to form an image on a paper sheet in accordance with print job data, the image forming unit including a rotating member as a component,
 the program comprising: 
 a rotation position detecting step of detecting a rotation position of the rotating member; 
 an image density detecting step of detecting a density in an image formed on an image carrier by the image forming unit; 
 an image information analyzing step of analyzing image information included in the print job data; 
 a density profile managing step of forming a correction patch image on the image carrier, and creating and managing a density profile indicating periodical density unevenness in accordance with a result of the detection performed in the image density detecting step with respect to the correction patch image; 
 a correction data creating step of creating correction data corresponding to the rotation position of the rotating member in accordance with the density profile; 
 a density correcting step of performing density correction using the correction data; and 
 a density correction control step of predicting an appearance of periodical density unevenness in accordance with image information about the image to be formed, and setting conditions for the density correction in accordance with a result of the prediction; 
 wherein the density correction control step includes extracting image regions from the image, determining a reference image region in accordance with lengths of the extracted image regions in a sub-scan direction and densities in the extracted image regions, and setting the conditions for the density correction in accordance with the length of the reference image region in the sub-scan direction and the density in the reference image region; 
 wherein the density correction control step includes determining whether to update the correction data, in accordance with the length of the reference image region in the sub-scan direction and the density in the reference image region; and 
 wherein the density correction control step includes updating the correction data when the length of the reference image region in the sub-scan direction is equal to or greater than a cycle length of the rotating member, and a difference between the density in the reference image region and a reference density is equal to or smaller than a predetermined threshold value. 
 
     
     
       7. The non-transitory recording medium storing a computer readable program according to  claim 6 , wherein the image information includes size information, color information, density information, and page information about the image included in the print job data, and size information about the paper sheet on which the image is to be formed. 
     
     
       8. The non-transitory recording medium storing a computer readable program according to  claim 6 , wherein the density correction control step includes updating the correction data when the length of the reference image region in the sub-scan direction is equal to or greater than a cycle length of the rotating member, a difference between the density in the reference image region and a reference density is equal to or smaller than a predetermined threshold value, and an area ratio of the density in the reference image region is equal to or higher than a predetermined threshold value. 
     
     
       9. The non-transitory recording medium storing a computer readable program according to  claim 6 , wherein the density correction control step includes setting a length of the correction patch image in accordance with the length of the reference image region in the sub-scan direction, when updating the correction data. 
     
     
       10. A non-transitory recording medium storing a computer readable program to be used in an image forming apparatus including an image forming unit configured to form an image on a paper sheet in accordance with print job data, the image forming unit including a rotating member as a component,
 the program comprising: 
 a rotation position detecting step of detecting a rotation position of the rotating member; 
 an image density detecting step of detecting a density in an image formed on an image carrier by the image forming unit; 
 an image information analyzing step of analyzing image information included in the print job data; 
 a density profile managing step of forming a correction patch image on the image carrier, and creating and managing a density profile indicating periodical density unevenness in accordance with a result of the detection performed in the image density detecting step with respect to the correction patch image; 
 a correction data creating step of creating correction data corresponding to the rotation position of the rotating member in accordance with the density profile; 
 a density correcting step of performing density correction using the correction data; and 
 a density correction control step of predicting an appearance of periodical density unevenness in accordance with image information about the image to be formed, and setting conditions for the density correction in accordance with a result of the prediction; 
 wherein the density correction control step includes separating the image into respective color components, and setting the conditions for the density correction for each of the color components.